This is a bug that might be too difficult to fix; I don't know, but I thought I'd report it anyhow so that at least people were aware of it.

If you have added fields to the orders_products table (as, for example, the dropship module does), edit orders will lose those fields. On an edit - even an edit as small as changing the order status - edit orders deletes and re-adds the orders_products table records. Since it is unaware that these additional fields exist, they are added back with their default values.